Add session shell and close world presentation follow-ups

Session shell
- Startup venue menu (src/game/ui/start_menu.gd): keyboard + mouse, replaces
  the live-shift boot and V as the player-facing venue path (V stays a debug bind).
- Pause overlay on Esc (src/game/ui/pause_overlay.gd): resume, restart shift,
  settings, quit to menu.
- Settings panel (src/game/ui/settings_panel.gd): mouse look sensitivity and
  HUD font scale, persisted via Save into user://settings.json and loaded on boot.
- Shift review "Run another shift" now returns to the venue menu.
- New smoke: src/test/smoke_session_shell.gd (menu -> shift -> pause -> settings
  -> menu), passes headless and windowed.

World and presentation
- Skyline backdrop restored with a transparent asset and an alpha-scissor
  unshaded material; fixes the opaque black slab from the earlier attempt and
  the unimported texture path.
- Steps and landing are a StaticBody3D with per-tread colliders, so the guard
  and NPCs walk up instead of clipping through.
- Marquee Label3D scaled up (72 -> 160) so STEP LINE reads from the sidewalk.
- Focus torus and name tag enlarged for 2-3 m readability.
- Routine traffic despawns after an idle lifetime (NpcAvatar.ephemeral), so the
  16-NPC cap no longer fills with standers; authored events stay for the shift.

Docs and tests
- PLAN.md test/CI section corrected to the custom headless runner and Gitea Actions.
- README controls table, smoke checklist, test count, and status lists refreshed.
- TODO/DONE/MEMORY updated; completed sections moved to DONE.md.
- Headless suite 77 -> 88 passing (settings round-trip, step colliders, skyline
  alpha, session-shell UI behavior, traffic lifetime).

MEMORY.md

@@ -16,15 +16,15 @@ Session memory for durable decisions, state, and gotchas. Keep concise, remove o
 ## Handoff (read this first)
 
 - Repo: `/run/media/system/DATA/Documents/06-games/security-game`. Godot: `~/.local/bin/godot` (4.3.stable).
-  Tests: `godot --headless --path . --script res://src/test/test_runner.gd` → **77/77**.
+  Tests: `godot --headless --path . --script res://src/test/test_runner.gd` → **88/88**.
+  Session shell smoke: `godot --headless --path . --script res://src/test/smoke_session_shell.gd` → exit 0.
   Windowed control smoke: `godot --path . --script res://src/test/smoke_focus_radial.gd` → exit 0.
-- `main` is **7 commits ahead of origin**, all committed locally, **not pushed**. The newest commit
-  is the control pass + boot/spawn fixes (access loadout, focus cone, action wheel, named input
-  actions, NPC rig, camera/building fixes, scheduler rate, NPC cap, screenshots, docs).
-- Nothing is left uncommitted. Ask before pushing if you did not author the earlier commits.
-- Next work, in order: (1) session shell in `TODO.md`; (2) world follow-ups listed at the top of
-  `TODO.md` (guard floats ~0.5 m, step colliders, skyline asset, marquee size); (3) push / release
-  when the user asks.
+- `main` is ahead of origin, all committed locally, **not pushed**. The working tree additionally
+  holds the session-shell + world-follow-up batch (start menu, pause overlay, settings persistence,
+  step colliders, skyline alpha, marquee/ring scale, traffic despawn, README/PLAN/TODO refresh).
+- Next work, in order: (1) remaining PLAN verbs in `TODO.md` (eye contact, recognize decision,
+  warning body-cam flag, blocking station, request reason); (2) crowd presentation (rubberneck +
+  evacuation); (3) `git add -A` + commit, push / release when the user asks.
 - Do not re-open `override_access`. Do not bind wand to `W`. Do not remove the radio easter egg.
 
 ## Current State
@@ -46,7 +46,24 @@ Session memory for durable decisions, state, and gotchas. Keep concise, remove o
   spawns in front of the door facing the street; building volume moved to z ∈ [-8,-4] so the door,
   awning, and marquee are visible; step treads rise toward the door; `ShiftCoordinator` pulls the
   event scheduler once per simulated second (was every physics frame → >1200 NPCs in seconds);
-  `GameManager.MAX_LIVE_NPCS = 16` caps live avatars; skyline backdrop removed (opaque black asset).
+  `GameManager.MAX_LIVE_NPCS = 16` caps live avatars.
+- **Session shell (2026-10-31, uncommitted):** the game now boots into `StartMenu`
+  (`src/game/ui/start_menu.gd`, layer 20) instead of a live shift. `GameManager._on_venue_selected()`
+  builds the scenario and calls `_start_shift()`; `_shift_running` gates input and `_refresh_freeze()`.
+  Esc with nothing open now pauses (`PauseOverlay`, layer 18) → resume / restart / settings /
+  quit-to-menu. `SettingsPanel` (layer 22) writes `look_sensitivity` + `hud_font_scale` through
+  `Save.save_settings()` → `user://settings.json`; `Save.load_settings()` merges over
+  `Save.DEFAULT_SETTINGS` on boot and `GameManager._apply_settings()` pushes them into the guard/HUD.
+  Shift review "Run another shift" now calls `_show_start_menu()` (not a silent restart). `V` stays a
+  debug venue bind. Smoke: `src/test/smoke_session_shell.gd` (menu → shift → pause → settings → menu).
+- **World follow-ups closed (2026-10-31):** skyline backdrop restored with `T_SKYLINE`
+  (`assets/textures/skyline.png`, regenerated RGBA with a transparent sky) and an
+  `TRANSPARENCY_ALPHA_SCISSOR` unshaded material (`_skyline_mat`); steps + landing are a
+  `StaticBody3D` with per-tread `BoxShape3D` colliders; marquee `font_size` 160 / outline 24; focus
+  torus 0.26–0.34 + name tag 48px; `NpcAvatar.ephemeral`/`lifetime_s` despawns routine traffic
+  (authored events stay). Guard spawn height verified on the landing (guard_y=0.84).
+- **Asset gotcha:** `assets/textures/game_ready/` is *not* imported (no `.import`). Use the
+  imported `assets/textures/skyline.png` path. Untracked duplicate folder should not be referenced.
 - Host sign-in follow-up remains deferred. PLAN.md + ADRs 0007–0010 still describe the intended UX.
 - **Release v0.2.1 is LIVE** (2026-10-31): CI run 1110 built the NSIS installer + AppImage
   and published — installers/AppImage are on the releases page. Releasing = bump version → tag → push.